Question on hanging pictures

Hey so I recently purchased a nearly century house (1930) and I'm looking for some guidance. Walls all appear to be plaster and lath. So far we've been using either the stick on hooks for lighter things and carefully drilling for some heavier things. Ran into something tonight and wasn't sure what my options are.

Went to hang a mirror on an exterior wall, front of the house if that makes a difference. When I drilled into the wall with a small bit to start the hole I hit what I think is the exterior brick. Obviously couldn't get the bit into that and had to stop. I was expecting lath under the plaster, not brick. Is this normal and in any case any suggestions on how to proceed?

The other question, the previous owner left us with some small screw holes. We can cover some with paintings, but others we want to patch. Any suggestions? The holes are small, quarter inch or less.

Thanks!